Catalytic conversion of hydrocarbon oils



3am, M, 947. masons EASTMAN ETAL 2 9 CATALYTIC CONVERSION OF HYDROCAfiBON OILS Original Filed Sepi. 4, 1941 :00 r000 MODIFIED REYNOLDS NUMBER (033:: H3385 slsva NOQHVI) .LHDIBNM CHARLES RICHKER DUBOIS EASTMAN INVENTORS Patented Jan. 14, 1947 CATALYTIC CONVERSION OF HYDRO- CARBON OILS du Bois Eastman, Scarsdale, N. Y., and Charles Richker, Port Arthur, Tex., assignors to The Texas Company, New York, N. Y., a corporation of Delaware Continuation of application Serial September 4, 1941.

This application January 24, 1945, Serial No. 574,389

2 Claims.

This invention relates to the catalytic conversion of hydrocarbon oil to gasoline hydrocarbons suitable for motor fuel.

The invention broadly contemplates a process wherein feed hydrocarbons are heated to a catalytic conversion temperature and passed, while substantially in the vapor phase, through an active mass of solid catalyst with a relatively high lineal velocity of hydrocarbon flow through the reaction zone so as to maintain conditions of turbulent flow through the catalyst mass in the reaction zone.

In catalytic cracking a stream of oil in substantially vaporized form and heated to a conversion temperature in the range about 800 to 1100 F. is passed through a catalyst bed maintained at the conversion temperature so as to convert the oil to gasoline hydrocarbons. The conversion to gasoline hydrocarbons is accompanied with concomitant breakdown of a portion of the feed oil to gas and coke or carbonaceous material, which latter is deposited upon the catalyst. As a result of this carbonaceous deposit the activity of the catalyst, as measured by the percentage conversion to gasoline and gas, decreases. It has been customary to operate such a process with an exceedingly short conversion cycle or onstream time and thereafter terminate the flow of feed hydrocarbon through the catalyst bed, following which the bed is reactivated by passing therethrough a highly heated gas containing air or oxygen to burn off the carbon deposit and thereby restore the activity of the catalyst. In such operations, the operating cycle is such that the catalyst cracking chamber is oiistream for at least twice the period of time that it is onstream or is actually being used for the conversion operation.

As disclosed in our pending application, Serial No. 383,900, filed March 18, 1941, which has matured as Patent 2,378,292, improved results are obtained including greatly increased throughput and higher efficiency of operation of the plant by: (l) selecting a charge stock preferably relatively free from unsaturated constituents and which is relatively clean and of good color, namely, having a carbon residue of less than 0.2% and a color of less than 200'as measured on the Lovibond scale using a [2-inch cell; (2) employing a cracking catalyst of high and sustained activity; (3) prolonging the conversion cycle time or onstream time to a period not less than one hour or preferably of the order of about 8 to 20 hours or more; and (4) heating the feed oil to the conversion temperature under conditions such that it undergoes substantially no change in composition prior to contact with the catalyst (heating under conditions such that the soaking volume factor, determined in the manner described in the aforesaid Patent 2,378,292, does not exceed about 1.0 and is as low as possible, in the range about 0.05 and below). L

The present invention has to do With the discovery that carbon deposition upon the catalyst is influenced to a substantial extent by the conditions of fluid flow existing through the catalyst mass. These conditions which exert a critical influence upon carbon deposition can be defined by means of the formula for determining the modified Reynolds number, reference to which appears in an article entitled packed tubes,

by Chilton and Coburn, Ind. Eng. Chem., August,

1931, vol. 23, No. 8, pages 913-919.

This formula is as follows:

D UP R Z where R is the modified Reynolds number; Dp, is diameter of catalyst particles in feet;

U is average velocity in feet per second of fluid P is average density in pounds per cubic foot of fluid mixture flowing through the empty tube under the operating conditions of temperature and pressure;

Z is viscosity of the fluid mixture flowing through the empty tube in pounds per foot per second under the operating conditions of temperature and pressure.

The value Z in the foregoing equation is: determined by multiplying the absolute viscosity of the Pressure drop in v. a nt pe s by :m t ly stm form y: th spe cific gravity of thehydifocaijbon so that the l igh temperature viscositics of v the gas oil and :2 n pht n t m ef en oiseset eeonversion the effective 'viscosity of; such' mixture is:

, Reynolds number asdeterminedbythe foregoing formula has avalue; in the rangeab'outf100 to between modified Reynoldsnumber and yield of carbon, per cent by weight of the feed hydrolinealyelocities of hydrocarbon flow through the *catalyst bed.

3 reaction mixture in centipoises by the factor 0.000672.

The viscosity of hydrocarbons at the temperature of conversion may be determined by reference to the nomograph on page 608 of Industrial and Engineering Chemistry, vol. 28, No. 5 (article entitled High temperature viscosities of liquid petroleum fractions, by Watson, Wien and Murphy). Using this method of viscosity determination the viscosity of the reaction mixture in the usual catalytic cracking operation will be approximately 0.10 centipoise where agas oil having the characteristics indicatedbelow is being catalytically cracked at a temperature of about 950 F. to produce 40% by weight of naphtha also having the characteristics indicated below:

Referring to the nomographic chart; it, ,wilhbe found that a gas oil of th'e'foreg'o'ingcharacter will have a viscosity of about 0.19 centistoke at 950 F. while the naphtha will have a-viscosity of about 0.09 centistoke at 950 F.

1 V sco e i es i eo vert dtdviseos y temperature will be:

On the basis that the reaction mixture com prises 50% gas oil and 40% naphtha by weight,

0.l66 .60=.0996 centipoise 0.060 .40 -.0 264 centipoise .1260 centipoise Thefq fegoing calculation ignores the presence 0f normally gaseous hydrocarbons in, the reactionmixture, the presence of which will reduce a the effective viscosity. somewhat so. that a value of .10 centipoise maybe regarded as substantially I representative, of the viscosityhof the. reaction ,mixtureunder the conditions specified.

through th epatalystbed such that the; modified 60 This is borne out by-the graphicalrelationship carbon -shown in the accompanying}- drawing. The curve of this drawing is plotted-on log log -paper and the points on the curve were de- ,aitrmined-in a series 'ofruns employing the same 10 type of feed oil with the same catalyst under substantially similar conditions -of temperature, pressure and space velocity but, with different 4 v The feed oil comprised a mixed base virgin gas oil having the following characteristics:

A. P. I. gravity degrees 30 Color, /2 inch Lovibond '15 Carbon residue per cent-.. 0.04 A. S. T. M. distillation:

I. B. P., F 434 10% 524 554 578 40% 602 658 694 9% 726 760+ In eachinstance the gas oil was passed in a .;i.eontinuous,.stream through a coil heater under p, x 5 pounds per square inch gauge wherein it ,eated to a temperature of 950 F. and while in substantially the vapor phase passed -through acatalystbed comprising alumina, silica ndq zirconianhaving a composition of approxi- "mately "20%a'1umina, 70% silica and 5% zirconia. .,The' catalyst comprised cylindrical pellets oneeighth of an inch in diameter and in length, the mass having a free ,.space.of about .35%.-

. VariationIin- ,thenature of..fiuid flow. through the catalyst mass whilegnaintaining,thelsame space velocity. may be. accomplished. ,by altering [th depthand crossgsectional area of thecatalyst bed from run to run .or,by varying th sizefand shape of the catalyst. i

' In each run theoil was converted,to.3,0%.gasoline bylvolume of.the feed oil, the-gasoline .being characterized. by having a. Reid; ,vapor pressure ;of 9 pounds and an end boiling pointof400" F.

The onstream period extended over a. period of 4 hours :following. which the. catalyst was reactivated in .the .usual manner and again placedonstream, the operation being repeated, for a. .minimum ofsix cycles .under each lineal velocity condition.

. During each regeneratingcycle therate of flow of the oxygen containing regenerating. gases .fed tothereactorundergoing regenerationjwas held a at a constant measuredrate and thecomposition of the .gases rentering .and leaving the. reactor determined. at frequent intervals. f The quantity of carbonaceous. material removedfrom the catalyst during regeneration was ,.then.- determined,by

, integratingtheincrease in; carbon monoxide. and

carbondioxidegcontent. of. thegases .overthe re- "j igenera-tiner riod. nd;multiplyin -birt qua jtity' of;t ere eneratinefligas flused. ,l'flhese .deterinitiations were ,verified by .calculatingivthe, carbon deposition from .th consurnption.,of. oxygerndur- .,ing the. regeneratingperiod.

.i As. indicated on the .drawing,. thescu zve isgrela- .tiyfely'flatin the range Yand. abovegwhile below I. hisrangeit rises. rather. steeplytbward; the. verf tical. '[Thus,...in .the region below a;.. modified Reynolds .number. of .100 the, yield oiicarbon deposited on .the, catalyst in reases quite, rapidly,

; whereas inthe reg'ion abet/e100 therate ofphange in, carbon oleprfisitionv is relativelysmallwith .Variation in the;fluid1 fiow through the bed. Iniother. words, when operating. with conditions, ,flow

c rrespondin to. a.. ,modified.-Reyncld rn mbe n" t e an .l 0. andga q t e .e ;.ei. carb ,de'pq i edpn thee telx t eas .-.fr9m.ales uti. 5 pie b .wei ht2o raw.i e i;e j J It i a v nt eous t o e ate wi h'lte nql s numbers well" above the critical so as to minimize deposition. In the case of the foregoing curve a Reynolds number of about 40 would be in the critical region. r

The conditions of flow existing through the catalyst mass may be influenced to some extent by thei'size and shape of the catalyst particles, lumps or granules since the free space of the catalyst mass may vary from about 35 to 45% by volume of the reactor space occupied by the catalyst mass.

In the foregoing experiments a synthetic silicaalumina-zirconia type catalyst was used. However, it is contemplated that other catalysts may be employed. Various.acid-treated and metalsubstituted clays, such as the Super-Filtrols, are satisfactory. Likewise, the acid-treated and metal-substituted natural or artificial zeolites, such as the artificial zeolite known as Doucil, can be used. Various metals can be substituted in the clays or zeolites, such as uranium, molybdenum, manganese, lead, zinc, zirconium, nickel and the like. Likewise the combination of certain acidtreated active clays of the'character of Filtrol, together with added proportions of alumina or silica or both can be employed. Alumina alone may be used under certain conditions. The synthetic silica-alumina catalysts can be improved by the addition of other constituents, such as zirconium oxide or molybdenum oxide. Other catalysts which are not silica-alumina catalysts, either synthetic or prepared from natural minerals, have been found which satisfy the characteristics of the catalyst of the present inven tion. Examples of other suitable catalysts comprise metallic halide compounds such as the halides of aluminum and chromium, etc. In general, a catalyst is employed which is stable at high temperatures of the order of 1400 to 1600 F., as determined by calcining in a mufrle furnace at that temperature, and which is a measure or indication of the ability of the catalyst to maintain its activity under the customary temperatures of reactivation of the order of 1100 to 1400 F., as measured by thermocouples within the catalyst bed during the reactivation cycle. It is preferred to employ a catalyst which is substantially free from alkali and alkaline earth metals.

Also if desired the conversion reaction may be carried out in the presence of light gases such as hydrogen and hydrogen-containing gases, including gases produced in the reaction and which may be recirculated through the heating and conversion zones or through the conversion zone only.

Although the invention has particular application in the conversion of gas oil and other high boiling hydrocarbons, it may be employed in effecting catalytic conversion of various types of hydrocarbons at elevated temperatures.

The present application is a continuation of our pending application, Serial No. 409,488, filed September 4, 1941, for Catalytic conversion of hydrocarbon oil.

Obviously many modifications and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated by the appended claims.

We claim:

1. In the catalytic cracking of a normally liquid heavier hydrocarbon oil charge to convert the same to gasoline hydrocarbons involving alternate periods of conversion and reactivation, the method which comprises continuously pass- "inga preheated and vaporized stream of heavier hydrocarbon oil charge stock having a carbon residue of less than 0.2% and a color of less than 200 on the Lovibond one-half inch scale through a contact mass or alumina silica-zirconia catalyst having acompositionof approximately 20% alumina, 70% silica and 5% zirconiajmaintaining the contact mass at a temperature of about 950 F. and under a pressure in the range atmospheric to about pounds per square inch gauge, maintaining conditions of hydrocarbon flow through the mass such that R has a value in the range 100 to 1000 as determined by the equation wherein P is the average density in pounds per cubic foot of fluid mixture flowing through the reaction chamber under the operating conditions of temperature and pressure;

Z is the viscosity of the fluid mixture flowing through the reaction chamber in pounds per foot per second under the operating conditions of temperature and pressure;

continuing the flow of said stream through the contact mass without intervening reactivation for a period of at least several hours onstream, 0btaining a, substantial naphtha yield with a carbon yield of not in excess of about 0.55% by weight of the feed oil, thereafter discontinuing the flow of the hydrocarbon charge in contact with said catalyst, reactivating the catalyst in situ and then repeating the process.

2. In the catalytic cracking of a normally liquid heavier hydrocarbon oil charge to convert the same to gasoline hydrocarbons involving alternate periods of conversion and reactivation, the method which comprises continuously passing a preheated and vaporized stream of heavier hydrocarbon oil charge stock having a carbon residue of less than 0.2% and a color of less than 200 on the Lovibond one-half inch scale through a contact mass of alumina-silica-zirconia catalyst having a composition of approximately 20% alumina, 10% silica and 5% zirconia, maintaining the contact mass at a temperature in the range 800 to 1000 F. and under a pressure in the range atmospheric to about 100 pounds per square inch gauge, maintaining conditions of hydrocarbon flow through the mass such that R has a value in the range 100 to 1000 as determined by the equation wherein R is the modified Reynolds number;

D1) is the diameter of catalyst particles in feet;

U is the average velocity in feet per second of fluid mixture flowing through the reaction chamber, the reaction chamber being regarded as emp y;

P is the average density in pounds per cubic foot of fluid mixture flowing through the reaction chamber under the operating conditions of temperature and pressure;

Z is the viscosity of the fluid mixture flowing -through the reactiomchamber' in mounds"per yie'ld of not: in :excess of'-abouth0;55% by weight foot 'pemsecond u der the op inmco ditions bf'the feed-oiL thereafter discontinuing the fiow r: :ofatemperature:andipressure -'---'=of 'thehydrocarbon charge' incontact with said continuing t w i t -th u th catalygt, reactivating the catalyst 'in'situ and then ,contact mass'withoutintrvenipg' reactivation for *repeatmgthepmcesa a periodmi at' 1east4severa1 hours onstre'amrob- V nU'BOIS EASTMAN.

;:tainipg a: substantialnaphtha yield with a." oarbon CH I 

